The invention relates to a method and apparatus for dynamically check weighing objects that are guided across a weight-sensitive zone of a weighing device with a conveying mechanism, wherein at regular intervals the weight-sensitive zone supplies individual measured weight values from which resulting weight values are derived in a digital evaluation unit by calculating mean values.
The invention further relates to an apparatus for dynamically check weighing objects comprising                a weighing device having a weight-sensitive zone,        a conveying mechanism that guides the objects across the weight-sensitive zone of the weighing device,        wherein the weight-sensitive zone at regular intervals supplies individual measured weight values from which a digital evaluation unit derives resulting weight values by calculating mean values.        
Methods and apparatuses of this type are known from DE 103 22 504 A1 and its published US counterpart US 2007/0181349 A1, which is incorporated into the present application by reference. This published document discloses a so-called check weigher and a method for setting and operating it. “Check weigher” is understood to mean a weighing device in which objects are conveyed to the weight-sensitive zone more or less continuously by a conveying mechanism in order to weigh them there. The weighed objects are then transported further by the conveying mechanism, to, e.g., be sorted according to the weighing result. A typical field of application of such check weighers is the final inspection and testing of nominally uniform objects. Examples would be the final fill level inspection of canned goods or a package sorting system.
A fundamental problem in such systems is finding a satisfactory compromise between weighing accuracy on the one hand and weighing speed on the other. In addition, systems of this type typically operate with strong interferences in an industrial environment. A typical setup, for example, conveys the objects by a fast-running conveyor belt that transfers the objects to a separate conveyor belt section, which is supported on the weight-sensitive zone of the weighing device and transfers the objects to another conveyor belt section after weighing. In systems of this type, the weighing signal is superimposed by significant interferences firstly from the movement of the conveyor belt, secondly from the fact that the object is lying only partly on the conveyor belt section supported on the weighing device when entering and leaving this section, and thirdly from various other vibrations that arise in the industrial environment. It has therefore proven worthwhile to record a large number of individual measured weight values for one object and derive a resulting weight value by suitable calculation of a mean value, rather to than determine a single measured value. In the above published document, the mean value is formed over a particular section of the sequence of individual measured weight values. The optimum position and length of the averaging section is found by “automatic” trial-and-error as part of a pre-setting procedure in which a large number of objects are weighed while the parameters for the section are varied. of the selected parameters for the section are then retained for the succeeding checking operation of the system.